This study was undertaken to seek evidence of natural selection with respect to human behavioral characteristics. The population chosen consisted of about 13,000 German-speaking Mennonites whose culture resembles in many respects that of pre-industrial European peasants. A cencus-survey was made in 1967 and vital records of the church were copied. For 569 families in the file, date include complete vital records and factor scores on several dimensions of social and economic behavior. Lengthy editing processes have now been completed and final analysis is in progress. This will first, specify parameters of survival and reproduction; second, explore interrelations among vital events such as effect of infant mortality on birth intervals; third, examine the effects on fertility of such variables as wealth, medical care, and social status.